Breast cancer is a significant health problem in both developed and developing countries. It is estimated that each year worldwide the disease is diagnosed in over 1,000,000 women and is the cause of death in over 400,000 women. Early detection provides a means to reduce the mortality of this disease as well as providing more treatment options and in many cases these options are less costly. While there are many treatment options available, including surgery, chemotherapy, radiation therapy, and hormonal therapy early detection improves the outcomes of the treatments.
The standard method for detection of breast cancer is mammography. However mammography can cause significant patient discomfort and requires radiation exposure. A lifetime cumulative exposure to radiation can in itself be a cause of cancer so a cost-benefit of mammography needs to be determined. Optical elastography is a method of changing the determination as the radiation exposure risk is eliminated. Furthermore, there are often variable results and inconsistencies in reading and interpreting the images of breast tissue from the X-Ray machine especially for smaller tumor sizes of the order of 1-5 mm. There has been a transition to other approaches, such as tomosynthesis and MRI, but tomosynthesis subjects the patient to as much, if not more, radiation, and MRI is extremely expensive and time-consuming.
Optical elastography is an emerging technology for non-invasive breast cancer screening without the requirement of radiation. Optical elastography is also different than standard elastography as it utilizes extremely low frequencies and the examination requires digital photography. Digital Image-based Elasto-Tomography is referred to herein as the DIET system. This technology is described in U.S. Pat. No. 8,249,691, issued Aug. 21, 2012, to Chase, Hann and Ray, entitled “Global motion invariant signatures for fast and accurate motion tracking in a digital image-based elasto-tomography system.” The DIET system uses a precise protocol of digital images of an actuated breast surface to determine tissue surface motion. It then localizes regions of internal tissue stiffness from that motion. Regions of high stiffness suggest cancer since cancerous tissue is between 3 and 10 times stiffer than healthy tissue in the breast. The method does not eliminate the value of mammography or other more detailed cancer detection methods, but is rather the first step in a triage of techniques. Like most first steps in a triage, it is intended to be fast, less invasive and inexpensive, but eliminate from further tests those women that are clear from cancer. The DIET approach also reduces the discomfort experienced in mammography from breast compression, leading to a higher likelihood of compliance. Moreover, screening could start with younger women and enjoy greater compliance.
Since the DIET system, is based upon digital imaging and software analysis it is designed for low cost and portability. Hence, the technology could be used in any medical centers primary care facilities as well as in remote areas. In addition, as the capability and cost of the major components of the system reduce in cost yet improve in performance, the DIET system will also follow the same trend. This scalability of performance is not true for X-Ray or ultrasound based approaches.
The DIET system design is based upon capturing images of actuated breast tissue and making measurements from the images. Consequently the imaging system needs to be calibrated, both in terms of individual cameras as well as between the multiple cameras within the system. Since variations of the surface motion are key to assessing the health of the patient, high-resolution cameras are preferred. It is important that small perturbations and variations on the surface be measured accurately to ensure smaller tumors are not missed. Current implementations of DIET rely upon the patient's breasts being tagged with colored fiducial markers to assist in the analysis phase, and thus, colored cameras are required.
However, reducing or eliminating the requirement of fiducial markers will further reduce costs and time for the patient. Therefore, there exists a need for very high-resolution feature registration and motion tracking system that can accomplish the same clinical results without using fiducial markers. With such an approach, as opposed to the '691 Chase patent, there would no longer be a need to use color image capture.